In this situation you would need some human task management capability(probably WS-HT compliant) and a user interface to present the tasks to a user.
Your BPEL process would then interact with the WS-HT task service to manage the tasks that are presented to the users.
At present though we do not provide a WS-HT and UI capability. These are being considered for later releases, but will not be available in the near future.
Are there any news regarding the WS-HT and UI capability?
No unfortunately. The jBPM team have a WS-HT implementation but it does not have a web service interface - so its just the core engine that implements the WS-HT workflow - and they also have a UI to manage the tasks I believe.
The problem is that the person who was originally going to do the web service interface against this engine is no longer available. If you know anyone who would be interested in doing this work, then let me know - otherwise currently it is unscheduled.